DE112006000787B4 - Passive scanning devices, systems and methods - Google Patents

Abstract

An apparatus comprising: a MAC (media access control) module for processing packets in a multi-chain WLAN (wireless local area network) node; a first receive chain in the WLAN node coupled to the MAC module to maintain a WLAN link including the WLAN node; a second receive chain coupled to the MAC module and located along with the first receive chain in the WLAN node and unassigned to participate in the WLAN link; and a correlator processor coupled to the second receive chain to passively scan for at least one access point during a period in which the first receive chain maintains the WLAN link and selectively disable passive scanning as soon as an approximately minimum number of access points was detected.

Description

Technical area

Various embodiments described herein generally relate to wireless communication technology, including devices, systems and methods used to perform passive scanning while associated with an access point.

Background information

A wireless device that operates under an 802.11 specification from the Institute of Electrical and Electronic Engineers can authenticate itself to an access point and then "link" to the access point by registering as a node in the network. The wireless operation of the link may be analogous to plugging a network cable in a wired environment from a workstation into a network port (eg, a port on a hub, switch, or router). For additional information regarding IEEE 802.11 standards, refer to "IEEE Standards for Information Technology Telecommunications and Information Exchange" between Systems-Local and Metropolitan Area Network-Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY). , ISO / IEC 8802-11: 1999 "and related additives.

However, a wireless link can be broken more easily than a cable link, as a continuous link may depend on radio frequency (RF) signal conditions. Therefore, the linkage of the wireless device may be resolved when RF noise levels, signal strengths, or other RF signal parameters change. Similarly, the changing RF signal conditions may result in one or more additional access points (s) being detectable (apart from the access point with which a link exists). Thus, a wireless device may continuously evaluate signal strengths (or signal-to-noise ratios) within a work band and possibly change the access point to which it is linked ("reconnect"). This technique, known in the art as "passive scanning", can operate on beacon packets received from additional access points.

Passive scanning for additional access points, however, can take a considerable amount of time, especially for an active band comprising multiple channels. For example, in the five gigahertz band, passive 30-channel scanning may take three seconds or more, assuming a typical beacon interval of about 100 milliseconds. Since the wireless device interrupts the passive scan operation with processing necessary to maintain the current link, complete passive scanning of the active band in the background may take a minute or more to complete. Therefore, an active voice or data connection may exceed the time limit and be dropped if the current link is interrupted by a degraded RF signal state before the additional access point (s) are detected.

In US 6,047,175 For example, there is described a wireless communication method that uses an auxiliary receiver to selectively select different channels. For this purpose, the auxiliary transmitter scans continuously available channels, so that based on a noise level, the respectively best channel can be used for communication.

The problems described above are solved by an apparatus according to claim 1, a system according to claim 7, a method according to claim 12 and a machine readable medium according to claim 18. The dependent claims 2 to 6, 8 to 11, 13 to 17 and 21 relate to advantageous embodiments of the subjects of the independent claims.

Brief description of the drawings

1 Figure 10 is a block diagram of an apparatus and system according to various embodiments of the invention.

2 FIG. 10 is a flowchart illustrating several methods according to various embodiments of the invention. FIG.

3 is a block diagram of an article according to various embodiments of the invention.

Detailed description

The 1 includes a block diagram of the device 100 and the system 160 according to various embodiments of the invention. The various implementations may be operated to reduce a time required to perform a passive background scan for additional access points while maintaining a link to a current access point. The device 100 can a MAC module (media access control) 106 include to packages 108 on a multi-chain WLAN (wireless local area network) node 110 to process. The device 100 can also have a first reception chain 114 in the WLAN node 110 include. The first receive chain 114 can with the MAC module 106 be paired to a wifi link 118 using the WLAN node 110 maintain, such as linking to a first access point 122 ,

The device 100 can also have a second chain of reception 124 include that with the MAC module 106 is coupled and with the first chain of reception 114 is arranged together. That is, the second receive chain 124 in the WLAN node 110 may be provided and may not be assigned to the wi-fi link 118 participate. Note that a multi-input, multiple-output (MIMO) device may have one or more receive chains that are not used when operating in a legacy mode according to an IEEE 802.11 specification, and one of the unused ones Receiving chains may be the second receiving chain 124 include.

A correlator processor 130 can with the second chain of reception 124 be coupled. The correlator processor 130 may include processors, include portions of processors, or operate on processing cycles derived from other processors. Thus, the correlator processor 130 in its computing power between different versions of the device 100 vary. The correlator processor 130 For example, essentially one copy of a main digital signal processor (DSP) 132 include, which is used to connect to Wi-Fi 118 maintain. Alternatively, the correlator processor 130 include a less powerful beacon preamble correlator, possibly including a limited functionality device capable of a beacon packet 134 to detect and identify for the purpose of passive scanning.

The correlator processor 130 can switch to one or more second access point (s) during a period of time 136 scan when the first receive chain 114 the Wi-Fi link 118 with the first access point 122 maintains. The second access point (s) 136 can be formed by access points that are not connected to the wifi 118 that the wi-fi node 110 includes, participate. Some versions of the device 100 can use a voltage controlled oscillator (VCO) 140 include that with the second chain of reception 124 is coupled to a frequency of passive scanning 146 to control the reception chain.

Other versions can be executed. A system 160 For example, one or more of the devices 100 have a MAC module (media access control) to packets 108 in a WLAN node, a first chain of reception 114 to a wifi link 118 using the WLAN node 110 maintain a second chain of reception 124 and a correlator processor 130 include as previously described.

The system 160 can also be an omnidirectional antenna 168 include that with the second chain of reception 124 is coupled to one or more beacon packet (s) 134 from one or more second access point (s) 136 to recieve.

The MAC module 106 can with a correlator processor 130 be coupled, and the correlator 130 can after the second access point (s) 136 scan, with the second access point (s) 136 no participants in the WLAN connection 118 are. The correlator processor 130 can be programmed to receive the beacon package (s) 134 recognizing the second access point (s) 136 be received. Passive scanning can be done on all channels in a wireless band, for which the wireless node 110 is configured to be performed in less than about ten seconds.

Each of the previously described components can be implemented in a number of ways, including via software. Therefore, the device can 100 ; the MAC module (media access control) 106 ; the packages 108 . 134 ; the WLAN node (wireless local area network) 110 ; the Wi-Fi link 118 ; the access points 122 . 136 ; the correlator processor 130 ; the digital signal processor (DSP) 132 ; the voltage controlled oscillator (VCO) 140 ; the frequency 146 ; the system 160 and the antenna 168 here all are referred to as "modules".

The modules may include hardware circuits, single or multiprocessor circuits, memory circuits, software program modules and objects, firmware, and combinations thereof, as determined by the architect of the device 100 and the system 160 is desirable and appropriate for certain implementations of the various designs. Thus, the modules may be implemented in a system operating simulation package, such as an electrical signal simulation software package, a power usage and distribution simulation package, a capacitance-inductance simulation package, a power / heat dissipation simulation package, a signal transfer / signal reception simulation package, or any combination of software and hardware used to simulate the operation of various possible implementations may be included. For example, these simulations can be used to design, characterize or test the designs.

It should also be understood that the devices and systems of various designs may be used in applications other than those employing a spare receive chain and a correlator processor to reduce the amount of time necessary to provide passive background scanning for additional access points perform.

Thus, various embodiments of the invention are not limited in this manner. The representations of the device 100 and the system 160 are provided to provide a general understanding of the structure of various embodiments, and are not intended to serve as a complete description of all of the elements and features of devices and systems that could utilize the structures described herein.

Applications that may use the novel devices and systems of various designs include electronic circuits used in high-speed computers, communication and signal processing circuits, modems, single or multiple processor modules, single or multiple embedded processors, data switches, and application-specific modules including multilayer multichip modules. Such devices and systems may further be included as subcomponents within a variety of electronic systems, such as televisions, cell phones, personal computers, workstations, radios, video players, vehicles, and others. Some embodiments may include a number of methods.

The 2 is a flowchart showing several procedures 211 represents according to various embodiments of the invention. Such a procedure 211 can at block 231 begin to work a multi-chain WLAN node according to an IEFE 802.11 specification, and can at block 237 continue to maintain a WLAN link by means of a first receive chain in the multi-chain WLAN node.

The procedure 211 may also include it at block 245 allow reconnection by the WLAN node without a session, such as a Voice Over Internet Protocol. Phone talk to drop while the wireless node moves at a rate of less than about five kilometers per hour. This is about the speed with which a mobile user moves when he walks around. This can be achieved by at block 251 after one or more access point (s) different from the access point involved in the current WLAN link are passively scanned in a period in which the first receive chain maintains the WLAN link.

The passive scan process may use a second receive chain located in the WLAN node along with the first receive chain, wherein the second receive chain is unassigned to participate in the WLAN link. The procedure 211 it can be at block 257 further refrain from entering (eg, delaying) a power-saving mode while passive scanning is being performed, and may at block 265 maintaining a power control bit in a media access control header transmitted from the WLAN node in a reset state. The procedure 211 can at block 269 also include selectively inhibiting passive scanning when detecting a minimum number of access points.

The procedure 211 can at block 271 continue to disconnect the Wi-Fi link of the Wi-Fi node, and can at block 279 to associate the WLAN node with one of the access point (s).

The methods described herein need not be performed in the order described, or in any particular order. In addition, various activities described with reference to the methods set forth herein may be performed in a repeating, serial or parallel manner. Information, including parameters, commands, operands and other data, may be sent and received in the form of one or more carrier waves.

One skilled in the art will recognize the manner in which a software program may be launched from a computer-readable medium in a computer-based system to perform the functions defined in the software program. Various programming languages may be employed to produce one or more software programs designed to implement and execute the methods disclosed herein. The programs may be structured in an object-oriented format using an object-oriented language, such as Java or C ++. Alternatively, the programs may be structured in a procedural format by means of a procedural language, such as assembler or C. The software components may communicate by a number of mechanisms known to those skilled in the art, such as application program interface or inter-process Communication techniques, including remote procedure calls. The teachings of the various embodiments are not limited to any particular programming language or environment. Thus, other embodiments can be realized.

The 3 is a block diagram of an article 385 according to various embodiments of the invention. Examples of such embodiments may include a computer, a storage system, a magnetic or optical disk, any other storage device, or any type of electronic device or system. The item 385 can be one or more processor (s) 387 include, the with a machine-readable medium, such as a memory 389 (eg a memory comprising an electrical, optical or magnetic conductor) is / are coupled. The medium may contain related information 391 include (eg, computer program instructions, data, or both) which, when accessed, cause a machine (eg, the processor (s)) 387 ) maintains a link over a wireless local area network (WLAN) by means of a first receive chain in a multi-chain WLAN node.

Other activities may include passive scanning for at least one access point during a period in which the first receive chain maintains the WLAN link by a second receive chain located in the WLAN node along with the first receive chain, the second receive chain is not assigned to participate in the WLAN link. Additional activities may include selectively inhibiting passive scanning once an approximately minimum number of access points have been detected, and allowing reconnection by the WLAN node without dropping a voice over Internet Protocol telephone conversation while the WLAN node is moving at a rate of less than about five kilometers per hour.

Implementing the devices, systems, and methods disclosed herein may reduce the amount of time required for passive scanning for additional access points, the use of a spare receive chain, and the use of passive scan clocking by a correlation processor ,

Although the inventive concept may include implementations in the exemplary context of an 802.xx implementation (eg, 802.11, 802.11a, 802.11g, 802.11n, 802.11 HT, 802.16, etc.), the claims are not limited in this regard , Embodiments of the present invention may be implemented as part of a wired or a wireless system. Examples may also include embodiments that include multi-carrier wireless communication channels (eg, OFDM, DMT, etc.), such as in a wireless personal network (WPAN), a wireless local area network (WLAN), a wireless city network (WMAN), a wide area wireless network (WWAN), a mobile network, a third generation (3G) network, a fourth generation network ( 4G ), a universal mobile telecommunication system (UMTS) and similar communication systems without restrictions.

The accompanying drawings, which form a part hereof, show by way of illustration and not limitation specific embodiments in which the article may be practiced. The illustrated embodiments are described in sufficient detail to allow one skilled in the art to apply the teachings disclosed herein. Other embodiments may be used and derived therefrom so that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Therefore, this Detailed Description should not be construed in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with a full scope of equivalents to which such claims are entitled.

Such implementations of the inventive subject matter may here, for convenience only, and without voluntarily limiting the scope of this application to any single invention or inventive concept, when more than one is disclosed, be individually or collectively referred to as "invention." , Thus, although specific embodiments have been illustrated and described herein, any arrangement that is intended to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of the various embodiments. Combinations of the above and other embodiments not specifically described herein will be apparent to those skilled in the art upon reading the above description.

The summary of the disclosure is given to describe 37 C.F.R. §1.72 (b), which requires a summary that allows the reader to quickly ascertain the nature of the technical disclosure. It is provided on condition that it is not used to interpret or limit the scope or meaning of the claims. In addition, it can be seen from the foregoing Detailed Description that various features are grouped together into a single embodiment for the purpose of facilitating the disclosure. This method of disclosure should not be interpreted as requiring more features than are expressly recited in each claim. Instead, the inventive subject matter may be found in less than all features of a single disclosed embodiment. Therefore, the following claims are hereby included in the Detailed Description, with each claim representing a separate embodiment per se.

Claims (19)

Apparatus comprising: a MAC (Media Access Control) module to process packets in a multi-chain WLAN (Wireless Local Area Network) node; a first receive chain in the WLAN node coupled to the MAC module to maintain a WLAN link including the WLAN node; a second receive chain coupled to the MAC module and located along with the first receive chain in the WLAN node and unassigned to participate in the WLAN link; and a correlator processor coupled to the second receive chain to passively scan for at least one access point during a period in which the first receive chain maintains the WLAN link and selectively disable passive scanning as soon as an approximately minimum number of access points is detected has been. The device of claim 1, wherein at least one access point is not included in the current WLAN link. The device of claim 1, further comprising: a voltage controlled oscillator coupled to the second receive chain to control a passive receive chain scan frequency. The apparatus of claim 1, wherein the correlator processor comprises a digital signal processor. The apparatus of claim 1, wherein the correlator processor comprises a beacon preamble correlator. The apparatus of claim 1, wherein the WLAN link operates in a precursor mode according to an 802.11 specification of the Institute of Electrical and Electronic Engineers. System comprising: a MAC (Media Access Control) module to process packets in a multi-chain WLAN (Wireless Local Area Network) node; a first receive chain in the WLAN node coupled to the MAC module to maintain a WLAN link including the WLAN node; a second receive chain coupled to the MAC module and located along with the first receive chain in the WLAN node and unassigned to participate in the WLAN link; a correlator processor coupled to the second receive chain to passively scan for at least one access point during a period in which the first receive chain maintains the WLAN link and selectively disable passive scanning as soon as an approximately minimum number of access points is detected has been; and an omni-directional antenna coupled to the second receive chain for receiving at least one beacon packet from the at least one access point. The system of claim 7, wherein the at least one access point is not included in the WLAN link. The system of claim 7, wherein the MAC (media access control) module is coupled to the correlator processor. The system of claim 7, wherein the correlator processor is programmed to recognize beacon packets from the at least one access point. The system of claim 7, wherein passive scanning is performed on all channels in a WLAN band for which the WLAN node is configured in less than about ten seconds. A method comprising: Maintaining a WLAN (wireless local area network) link by means of a first receive chain in a multi-chain WLAN node; and passive scanning for at least one access point during a period in which the first receive chain maintains the WLAN link by means of a second receive chain located in the WLAN node along with the first receive chain, the second receive chain not being assigned to join the Wi-Fi link; and selectively inhibiting passive scanning once an approximately minimum number of access points have been detected. The method of claim 12, wherein the at least one access point is not a subscriber to the WLAN link including the WLAN node. The method of claim 12, further comprising: Refrain from entering an energy-saving mode while passive scanning is being performed. The method of claim 12, further comprising: Disconnecting the WLAN node from the Wi-Fi link. The method of claim 12, further comprising: Link the WLAN node to one of the at least one access points. The method of claim 12, further comprising: Operation of the WLAN Node According to an 802.11 Specification of the Institute of Electrical and Electronic Engineers. A machine readable medium having linked information, the information, when accessed, causing a machine to execute: Maintaining a WLAN (wireless local area network) link by means of a first receive chain in a multi-chain WLAN node; passive scanning for at least one access point during a period in which the first receive chain maintains the WLAN link by means of a second receive chain located in the WLAN node along with the first receive chain, the second receive chain not being assigned to join the Wi-Fi link; and selectively inhibit passive scanning once an approximately minimum number of access points have been detected. The machine readable medium of claim 18, wherein the information, when accessed, results in a machine performing: Allowing the reconnection by the WLAN node without dropping a voice-over Internet Protocol telephone conversation while the WLAN node is moving at a speed of less than about five kilometers per hour.

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